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By G. Bräuner

The methods of burst control treated in the authors' very informative paper have been applied in the Ruhr Coalfield, Germany, for more than 20 years and have proved to be highly effective. It might be interesting here to mention a few experiences: • The symptoms of critical stresses when drilling with small diameters ("test drilling") are essentially the same as described. However, we consider the situation safe if these symptoms occur beyond a certain distance ahead of the face. • That safety distance equals three times the seam thickness plus the daily advance. It is the total seam thickness that counts, not merely the mined portion. • Critical stresses within the safety distance are dissolved by so-called destressing measures: drilling with heavier equip¬ment, blasting, or water infusion. • To avoid bump initiation, the destressing operations should begin at the sides of the stressed zone rather than in the middle. • As to water injection, there are two different principles. If the situation is critical already, high pressures are applied for hydraulic fracturing. If the stresses still allow to drill deep holes, the fluid pressure is kept low and acts for a longer time. This is to make the coal break successively instead of violently - a long-term precaution. • When the stresses are very high, destressing is the most appropriate means. We mostly drill with 95 mm-diam (3.7 in. - diam). The techniques in detail are somewhat complex and sub¬ject to modifications. But the general idea is to accomplish burst prevention by controlling the potential burst situations.

Jan 1, 1989

By G. Le Bel

The paper proposes three methods to determine optimum lifetime of a mining project1. The conclusion is that the three methods arrive at the same optimum production rate (by coincidence). It is also stated that: "The stochastic and option pricing models, in addition to providing a more realistic optimum mine life than the traditional NPV (net present value) calculation, showed that the example project has the potential for substantially higher return. By explicitly considering a project's potential risks, the stochastic or option pricing techniques can more accurately describe its probable investment performance." This discussion is intended to demonstrate that: • It is no coincidence that the three methods arrive at the same optimum production rate. • The stochastic and option pricing models do not provide a more realistic optimum mine life than the traditional NPV calculation. • The potential for a substantially higher return is misrepresented. First, a review of investment decision theory in mining is needed. Net present value is the preferred performance measure because of the flexibility offered when comparing various alternatives. However, it presents the following disadvantages: • The discount rate selection is not straightforward. • The NPV obtained represents a deterministic characterization of the variables included in the cash flow calculations, i.e. a single-point estimate.

Jan 1, 1993

By J. P. Zannaras

Referring to the article by R. J. Charles and P. L. de Bruyn, let us assume that W = weight of glass bar; P = weight of hammer; e = total deformation; E = unit of deformation; K = potential stress energy; E = modulus of elasticity; L = length of the bar; 7, = coefficient of inertia; h = height, ft; V = velocity, fps; and a = cross section area. The portion of kinetic energy which is effective in producing stress energy in a fixed bar struck horizontally is given by the formula [ ]

Nov 1, 1956

By S. Serata

Background Results of the above study in the August 1991 issue of Mining Engineering offer valuable lessons in the solution of cutter-roof problems. The original study plan was initiated by the discussion authors to solve the problems using the "stress control method" of mining (Serata 1976,1982; Serata, Carr and Martin, 1984; Serata and Gardner, 1986; Serata, Gardner and Preston, 1986; Serata, Gardner and Shrinivasan,1986; Serata and Kikuchi, 1986; Serata, Preston and Galagoda, 1987) However, the plan and the planner were changed to the arrangement reported in the paper. The change was considered reasonable at the time due to the mine engineers' uncertainties about the stress control method. Consequently, the basic principle of the study was shifted from the original stress control method to the method described in the paper, which will be called the "yield pillar method" for the purposes of this discussion. The paper convinces the reader that the yield pillar method fails to solve the cutter-roof problems. This doesn't mean that the stress control method also fails. Actually the contrary is true, as discussed below. Limitation of the yield pillar method The paper illustrates clearly how poorly the yield pillar method performs in solving the problem. The reason for this failure is the lack of the protective stress envelope needed to stabilize the cutter roof. Unfortunately, the protective envelope cannot be formed properly without utilizing the stress control method of mining. Changing the pillar size does not make much difference in the roof stability.

Jan 1, 1992

By John S. Rinehart, Norman Ahlquist

The model which Birkimer has developed to explain the increase in fracture strength of brittle, rock-like materials with increasing rate of loading may have some applicability. It should be noted that since his analysis presupposes elastic behavior he could equally well express his result as an increase of stress to fracture with increasing strain rate, a fact which is well known. Certainly his experimental results do not contradict his strain rate to the one third power law. On the other hand, we do feel that the data are insufficient and inadequate to establish the relation- ship definitely. 'In metals, the whole fracture picture is greatly complicated by concomitant plastic flow and, in rocks, by the presence of macroscopic flaws and inhomogeneties. Both lead to uncertainties as to the state of stress during the fracture process. He quotes in support of his theory Rinehartfs results on rock in which the latter found that under impulsive loading by explosives, rocks appear to be many times stronger than under static loading. We suspect that the observed increase has little specific relevance to the theory which Birkimer puts forward. Rinehart's measurements were made by spalling rocks using a sawtooth shaped stress wave of known intensity and duration. The rise time of such a pulse is essentially zero, certainly less than 0.1 microseconds, so that it is not possible to apply Birkimerfs theory quantitatively. We favor attributing the increase in fracture strength to two factors. First, the action takes place very quickly in an exceedingly thin region so that statistically the probability is small of encountering one or more of the large flaws that contribute so significantly to the reduction of strength of most rocks under tension. It is also conceivable that the compressive wave that has just passed by the region of fracture has strengthened the rock by collapsing some of the larger flaws. Second, the state of stress obtaining at the time of fracture is not all that existing when the

Jan 1, 1971

By E. J. Garrison

A.C. Noble presents a clear and concise summary of the factors pertinent to a competent reserve evaluation of a mineral occurrence. However, I believe that he confuses the difference between a resource and a reserve. By definition, a reserve estimate includes all known economic, legal, mining, metallurgical and environmental factors impacting the recovery of the product(s) found in the deposit. A resource estimate, however, is an estimate of what is there - what is available for exploitation and should not include economic and other considerations. Only after defining the resource, its extent, location, physical and chemical properties, can an intelligent selection process begin of the extraction and processing technologies most appropriate to the circumstances encountered. The early and almost certainly inappropriate application of these often cookbook choices has probably lead many companies to walk away from good properties. (How many mines have been found in others rejects?) An example of the process is the early selection of metallurgical samples, after encouraging values are found in a few holes or surface samples, in an attempt to determine the economics of the prospect. Unfortunately, the sampler does not know how representative of the occurrence the sample is because he does not know what the deposit looks like. As a consequence, the property becomes saddled with a bad metallurgical sample that is often inappropriately used in evaluating the deposit which it does not represent.

Jan 1, 1994

By D. G. Krige

I read the paper “The jackknife approach” with interest. There appears to be a widespread misunderstanding of the kriging variance as a measure of the error variance of the kriged grade estimate of an ore block. Virtually all mineral deposits display skew frequency distributions and are subject to the well-known proportional effect. Thus, it is usual to find in an ore body, when subdivided a really into subpopulations, that the variances of the grades (or the total sills of the variograms) for the subpopulations will be correlated with the corresponding mean grades (usually linearly with the squares of the mean grades). Thus, the variogram will be stationary.

Jan 1, 1996

By G. E. Agar

In the April issue of Mining Engineering there is a technical note "New size laboratory ball mill for Bond Work Index determination" written by M. Nematollahi which is very confusing. My recollection is that a description of an experimental procedure should be such that someone skilled in the art should be able to reproduce the results. Applying this test to this particular article would according to me cause a failure to be registered. There are apparently three batch laboratory test procedures referred to in the article. One of these is the traditional Bond test with all its limitations such as dry grinding followed by exclusively dry screening, two attributes which fail to simulate conventional industrial grinding. There is a second procedure (NSBM) which the author is advocating as an improvement of the Bond procedure but from the description I doubt that anyone would be able to repeat the procedure. For instance, is the grinding to be done wet or dry, if wet at what pulp density, and how is the screening to be done, wet or dry or a combination?

Jan 1, 1995

By J. A. Richardson

J. A. RICHARDSON[t]-Mr. Stuckey's account of the geology of the kaolins of North Carolina suggests that they exhibit some features similar to those of the Malay Peninsula. About one half of British Malaya (some 26,000 square miles) is occupied at the surface by igneous rocks, of which granite and its associated derivatives constitute fully 90 pct. The average granite is a biotic variety. It is predominantly potassic but carries, in addition, notable amounts of soda and lime so that albite and albiteoligoclase are generally common constituents of the rock. The minor derivatives from granite "magma" likewise include potassic and sodi-potassic members. Decomposition of the granitic rocks has led to the formation of kaolin in many localities, but, in general, the deposits are rather small and, at present, none is exploited commercially. True primary or residual kaolins (as defined by Stuckey; p. 48 Vol. 173, p. 2 TP 2219) have been developed from feldspar veins, pegmatites and from other granitic differentiates which cut through the larger masses of granite; they are usually small and narrow. Kaolin has been derived from aplite, quartz porphyry, quartz micro-porphyry, felsites and microgranites belonging to a complex known as the Chegar Perah-Pulai intrusion in northwest Pahang and southwest Kelantan. The bulk of the component rocks has been more or less strongly sheared. Kaolin-like end products have been formed from both sheared and nonsheared varieties. Kaolin has been formed also by the complete breakdown of trondjemite flanking the northwestern and western margins of the complex Bukit Ranjut syenite intrusion in northwest Pahang. These trondjemites range in composition from essentially quartz-free albiteplagioclasites to quartz-free microcline rocks; they are, in effect, the syenitic homologues of white sodic and potassic granite-aplites. The granites in Malaya have generally undergone more or less severe surficial weathering leading to the production of a spongy and rather cellular or a soft "mealy" material (sandy clay) down to depths of about 100 ft; in places the granite is strongly decomposed down to 150 ft. There has occurred, therefore, widespread partial kaolinization, but, in general, no extensive deposits of good quality kaolin seem to have been formed by these processes of decay. Frequently, the katamorphic processes of desilicification have advanced beyond the production of kaolin towards the formation of lateritic end products. The more important Malayan kaoiins seem to be confined to the western alluvial plains, particularly in areas either where granite crops out at surface, or where it forms the bedrock of the alluvium. There are numerous excellent examples around Gopeng and elsewhere in the Kinta Valley of Perak. Such kaolins belong to Stuckey's groups of secondary deposits, and, like them, these also may be bedded. Field observations have established the existence of what for want of a better name is referred to by the Malayan Geological Survey as "granite wash." It is believed that granite, undergoing extensive deeply penetrative and probably rather rapid destruction under humid tropical weathering (temperature around 90°F; rainfall about 100 in. per annum; high humidity) "flowed," was moved by "creep" and, in addition, probably slumped in large waterlogged masses of sandy clay from topographic salients onto the adjacent flats. Either during this period of transmigration or later when the sludged granite detritus, after having more or less come to rest, was attacked by flowing water, differential sorting and erosion took place with the result that the resorted debris was moved and later deposited as bedded alluvium. In this way, banded "granite wash" was produced comprising alternating bands of clayey sand (resorted granite sludge) and white

Jan 1, 1947

Minter's excellent recent paper (1990) on the great paleoplacer gold deposits of the Witwatersrand and its subsequent discussion (Cheney, 1991) and reply (Minter, 1991) provide an informative, interesting and up-to-date review of the geology of these unique ores and some long enigmatic questions regarding their origin. Clearly summarized by Minter (1990) are the compelling sedimentologic and stratigraphic relationships indicating that the Central Rand Group conglomerates are ancient placers and documenting the fluvio-deltaic conditions of their transport and deposition. As Minter (1991) indicates, Cheney's discussion broadens Minter's 1990 coverage of the subject by considering higher and lower stratigraphic units and by adding detailed comments concerning recently published information about metamorphic and age relationships. Cheney's discussion and Minter's reply also readdress the old controversy of epigenetic hydrothermal vs. syndepositional placer origin for these deposits. This controversy has been resurrected by: • recent recognition of hydrothermally-altered granites (HAGS) in the older Archean basement rocks that lie unconformably beneath the Dominion Group rocks north and west of the Witwatersrand depository; • recognition of greenschist metamorphic assemblages in the Witwatersrand strata; and • the presence of interpreted epigenetic mineral assemblages and textures in some of the deposits. These relationships are briefly discussed by Cheney who suggests they may result from later, superimposed metamorphism and deformation and do not prove that the gold was introduced by epigenetic/metamorphogenic processes. In his paper, Minter (1990) cited the 1986 abstract of a subsequently published paper by Hutchinson and Viljoen (1988) who also considered many of these aspects and attempted to integrate them all in a broad genetic hypothesis. In addition, they emphasized the additional important problem of determining the source for the Witwatersrand gold. Although this issue was partially addressed by Reimer (1984), Mossman and Dyer (1985) and Reimer and Mossman (1990), the question has been generally under emphasized in earlier work and was, therefore, not stressed by Minter and Cheney. Reimer (1985) also emphasized the importance of weathering of the basin's Archean hinterland and its affects on Witwatersrand sedimentation.

Jan 1, 1992

By D. Leppert

Mr. Garrett brings up several interesting points with respect to the proposed API specification for "nontreated bentonite." However, although not explicitly stated, these specifications are being written based strictly on bentonites from the Wyoming/South Dakota area. Other sodium bentonites may be suitable for use as drill mud but will be unacceptable since the specifications are designed for Wyoming bentonites. Regardless of the API's intent that its specifications are intended only as guidelines, they are generally adhered to on an international basis and, for practical purposes, might as well be chiseled in stone. Estes (1986) notes that the quality of bentonite available from Wyoming producers has steadily declined since the early 1960's. The plastic viscosity: yield point (PV:YP) ratio was included in the current API 13A specification primarily to prevent excessive polymer treatment of lower quality bentonites to make drill mud. However, with development of polymers designed to control YP, this specification cannot ensure that only high-quality bentonites are used for drill mud. Nor will the new specifications for untreated bentonites. Other sodium bentonites are available. Bentonite produced in southeast Oregon demonstrates superior performance characteristics without addition of polymer or other chemicals. However, the exceptionally high purity of these deposits leads to a relatively high YP:PV ratio since the naturally high YP probably results from the higher purity and smaller particle size of this bentonite (Rath, 1986 and personal communication). These bentonites typically have a smectite component exceeding 90% (Rath, 1985), compared with 70% to 75% smectite for typical Wyoming bentonites, as determined by X¬ray diffraction and tests for colloid content. As evident from the accompanying table, the untreated Oregon bentonite has excellent rheological properties, though different from Wyoming bentonites due to the high purity. Additionally, this bentonite reacts well with polymers typically used in the oil industry, making it eminently suitable for use in a low-solids mud system. The extremely low grit content, less that 0.5% on a 75 mm (200-mesh) wet sieve, greatly exceeds the standards set for Wyoming bentonite. Optimum rheological properties are obtained at a higher moisture content than Wyoming bentonites. At 10% moisture, API 13A maximum, the clay is overdried, again reflecting the high smectite content. In summary, the specifications proposed by the API Task Group will ensure that only Wyoming producers can supply "nontreated" bentonite to the oilfield since specifications are

Jan 1, 1989

By J. Parker

Gentlemen; Rainy day in Upper Michigan, a good time to catch up on reading. Am doing that, and have a couple of questions concerning the K and P paper on roof problems and supports. I wonder if the authors can enlighten me. The compressive strength of the coal was reported as 4.4 MPa (633 psi) and compressive stresses measured in the coal seam were reported at around 27.6 and 48.2 MPa (4000 and 7000 psi ). Can such a soft coal actually contain such a high level of stress? Can it be measured as if the material were elastic, or does the coal behave plastically? Can that stress level be confirmed with hydraulic load cells? And if the coal is so soft, and if it is plastic, why is the stress field not hydrostatic? The intact roofrock appears to be unusually strong, with compressive strength reported at around 145 MPa (21,000 psi), and some failures were noted as soon as the rock was exposed. Were tests run to find out how that rock responded to the addition

Jan 1, 1991

P. W. BRIDGMAN.-Owing to a misunderstanding, I did not see Dr. McAdam's and Dr. MacGregor's remarks on my paper on Flow and Fracture (Metals Technology, December 1944, Pp. 32-38), until after their publication. Both Dr. McAdam and Dr. MacGregor speak of my analysis for the stress distribution at the neck of a tension specimen as containing several assumptions; in particular, that the strain is uniform across the section of the neck, that there is no hoop tension at the periphery, and that the plasticity conditions of von Mises hold. As far as the mathematics goes, the situation is no different in this problem of plastic flow than in a conventional problem of elasticity. That solution is unique which satisfies the boundary conditions on the stresses, the stress equations of equilibrium, and in addition the constitutive equations connecting stress and strain in the elastic case, or a corresponding set of equations, of which the von Mises relations are a special form, in the plastic case. In the particular case of the necked tension specimen I have found that there is a solution satisfying the boundary conditions, the stress equations of equilibrium, and the von Mises plasticity conditions in which the strain is uniform across the section, and there is no hoop tension at the periphery. This is therefore the solution, and the uniformity of strain and vanishing of hoop tension at the periphery are to be described as discoveries, over which the operator has no control, rather than as assumptions. The only part of the solution that can properly be described as an assumption is the von Mises plasticity condition. With regard to this it is to be noted that the condition is needed only in a much weakened form, for the analysis uses the condition only at the neck, where the strain is approximately constant. Thus, in the extreme case referred to in a footnote of my paper (p. 37, Met. Tech. Dec. 1944) the actually measured strain across the section varies from 2.4 to 2.6. Obviously it is a much weaker assumption to postulate that the von Mises condition holds in the strain range 2.4 to 2.6 than to assume it to hold for the entire range of strain from o up to 2.6, which would be necessary if the solution applied to the entire tension specimen rather than to the immediate region of the neck only. Furthermore, it is to be commented that under the special conditions of this problem the von Mises condition becomes identical with the maximum shearing-stress criterion of plastic flow; this amounts also to a weakening of the restrictions imposed by the von Mises condition. Dr. MacGregor refers to actual experiments of his own in which the strain was found not to be uniform across the neck. It is to be emphasized, however, that these were experiments on bars of rectangular section, and that the nonuniformity established was a nonuniformity around the perimeter, not a nonuniformity from the surface toward the axis. My method of solution applies only to a circular cross section. It can be said that the solution that satisfies the boundary conditions, etc., would definitely not be expected to demand a uniform strain for noncircular sections. In discussing my results, Dr. McAdam uses a definition of "flow stress" different from mine, so that the immediate applica-

Jan 1, 1945

By Dan Plazak

The authors are to be congratulated for presenting a simple and practical tool for quick estimates of ground water flow rates. At the risk of detracting from the simplicity of the method, I would like to suggest a slight refinement to the equation as presented. As the authors noted, the Jacob-Lohman equation (1952) assumes confined-aquifer conditions. To use confined-aquifer equations in water-table aquifers, Jacob (1963) presented a correction to convert water-table aquifer drawdowns [ ] to equivalent confinedaquifer drawdowns [ ]:

Jan 1, 1994

Page The Cobaltchromium Binary System (paper by A. R. Elsea, A. B. \Yesterman, and G. K. Manning, Met. Tech. June, 1948, Mechanism of Precipitation in a Permanent Magnet Alloy (paper by A. H. Geisler and J. B. Newkirk, Met. Tech. Aug. 1948, Tp 2444)................................................................................................. 300 Some Effects of Applied Stresses on Precipitation Phenomena (~aper by W. L. Finlay and W. R. Hibbard, Jr., Met. Tech. Sept. 1948, Tp 2470)....................................................................................... 301 Diffusion of Carbon in Austenite with a Discontinuity in Composition (paper by L. S. Darken, Met. Tech. Sept. 1948, TP 2443) 304 An Electron Diffraction Study of Oxide Films Formed on Nickelchromium Alloys (paper by J. W. Hickman and E. A. Gul- bramen, Met. Tech. June 1948, Tp 2372)..................................................................... 305 An Electron Diffraction Study of Oxide Films Formed on Copper-nickel Alloys at Elevated Temperatures (paper by J. W. Hickman and E. A. Gulbransen, Met. Tech. June 1948, TP 2391)................................................ 307 Decarburization of Chrome Nickel Alloys by Their Surface Oxides in High Vacua and at Elevated Temperatures (paper by E. A. Gulbransen, W. S. Wysong, and K. Andrew, Met. Tech. Sept. 1948, TP 2438)................................ 307 Fractographic Study of Cast Molybdenum (paper by C. A. Zapffe, F. K. Landgraf and C. 0. Worden, Met. Tech. Aug. 1948, TP 2421)................................................................................................. 308 Effect of Composition on Grain Growth in Aluminum-magnesium Solid Solutions (paper by L. J. Demer and P. A. Beck. Met. Tech. June 1948, TP 2374)............................................................................. 309 Effect of a Dispersed Phase on Grain Growth in Al-Mn Alloys (paper by P. A. Beck, M. L. Holzworth and P. Sperry, Met. Tech. Sept. 1948, TP 2475)................................................................................. 310 Statistical Rate Theory of Metals—Mechanism of Flow and Application to Tensile Properties (paper by J. W. Fredrickson and H. Eyring, Met. Tech. Aug. 1948, TP 2423)............................................................... 315 Nucleation of Slip Bands (paper by J. G. Leschen, R. P. Carreker, and J. H. Hollomon, Met. Tech. Sept. 1948, TP 2476) and.. 318 Transient Plastic Deformation (paper by R. P. Carreker, J. G. Leschen, and J. D. Lubahn, Met. Tech. Sept. 1948, TP 2477).. 318 Plastic Deformation of Large Grained Copper Specimens (paper by W. R. Hibbard, Jr., Met. Tech. Sept. 1948, TP 2469). ... 323 Plastic Flow in Anisotropic Sheet Steel (paper by L. R. Jackson, K. F. Smith, and W. T. Lankford, Met. Tech. Aug. 1948, TP 2440)................................................................................................. 323 The Effect of Thermal-mechanical History on the Strain Hardening of Metals (paper by J. E. Dorn, A. Goldberg, and T. E. Tietz, Met. Tech. Sept. l948, TP 2445)....................................................................... 325 The Room and Elevated Temperature Properties of Some Sand Cast Magnesium-base Alloys Containing Zinc (paper by T. E. Leontis, Met. Tech. June 1948, TP 2371)..............................................................., 327 The Low Temperature Properties of Tin and Tin-lead Alloys (paper by H. S. Kalish and F. J. Dunkerley, Met. Tech. Sept. 1948, TP 2442)............................................................................................335 Thermal and Electrical Properties of Ductile Titanium (paper by E. S. Greiner and W. C. Ellis, Met. Tech. Sept. 1948, TP 2466).................................................................................................... 335 Property Changes during Aging (paper by A. H. Geisler, Met. Tech. Aug. 1948, TP 2436)............................... 337 Factors Affecting the Tensile Notch Sensitivity of Magnesium Alloy Extrusions (paper by I. Cornet, Met. Tech. Aug. 1948, TP 2419)................................................................................................. 338 Effect of Grain Size on Tensile Strength, Elongation and Endurance Limit of Deep Drawing Brass (paper by H. L. Walker and W. J. Craig, Met. Tech. Sept. 1948, TP 2478)............................................................. 339 A Copper-base Alloy Containing Iron as a High-strength, Highconductivity Wire Material (paper by W. Hodge, R. I. Jaffee, J. G. Dunleavy, and H. R. Ogden, Met. Tech. Aug. 1948, TP 2422).............................................. 340 A High Strength-High Conductivity Copper-silver Alloy Wire (paper by W. Hodge, R. I. Jaffee, J. G. Dunleavy, and H. R. Ogden, Mel. Tech. June 1948, TP 2366)...................................................................... 340 The Effect of Chronlium on the Ma Point (paper by J. B. Bassett and E. S. Rowland, Met. Tech. Aug. 1948, TP 2417.... 341 The Kappa Eutectoid Transformation in the Copper-silicon System (paper by W. R. Hibbard, Jr., G. H. Eichelman, Jr., and W. P. Saunders, Met. Tech. Sept. 1948, TP 2441).............................................................. 343 Stabilization of the Ausknite-martensite Transformation (paper by W. R. Harris, Jr. and M. Cohen, Met. Tech. Sept. 1948, TP 2446)................................................................................................ 344 Secondary Hardening of Tempered Martensitic Alloy Steel (paper by W. Crafts and J. L. Lamont. Mel. Tech. Sept. 194,8, TP 2439)................................................................................................. 345

Jan 1, 1950

By Evans E. C.

Discussion of the paper presented at the Manchester Geological and Mining Society' general meeting held in Manchester, March 14th , 1916, with Leonard R. Fletcher, President, in the Chair included contributions by Fletcher L.R., Paton J.D., Orchard A.J.A., Ross A., Gerrard J. and Stephenson H., with the author's responses

Dec 1, 1916

Discussion of the paper presented at the Manchester Geological and Mining Society's general meeting held in Manchester, April 11th 1916, with Mr. Leonard R. Fletcher, President, in the chair, included questions asked and points for discussion raised by Bramall V., Paton J.D., Fletcher L.R., Siddall F.N., Stoker A. and Stone T., in particular on how to eliminate dust

Dec 1, 1916

Discussion of the paper presented at the North Staffordshire Institute of Mining and Mechanical Engineers' general meeting held in Stoke-on-Trent, March 27th 1916, with Mr. John Gregory, President, in the chair, included contributions by Gregory J., Cadman J., Hartley J.W., Wain E.B. and Henshaw A.M., followed by the author's reply

Dec 1, 1916

By Gibson J.

Written discussion contributions to the paper presented at the North of England Institute of Mining and Mechanical Engineers' general meeting held in Newcastle-upon-Tyne, 12th February 1916, with Mr. T.Y. Greener, President, in the chair, comprise comments by Kilpatrick W.M., Routledge W.H., Watson J. and Smith W., along with the author's reply. Also briefly noted are the demonstration of two pieces of equipment, an incline chock and a cage arrestor

Dec 1, 1916

Jan 1, 1951